Last season, the men’s 110m Hurdles was all about the brilliance of Aries Merritt, but the 2013 campaign has been much less clear cut and at least half a dozen top athletes will have designs on winning the gold medal in Moscow.

Merritt, who described 2012 as the 'perfect year' as he landed the Olympic title and shattered the World record, strained a hamstring at the IAAF Diamond League meeting in Shanghai back in May and has been playing catch up ever since.

The 28-year-old athlete only just squeezed into the US team for Moscow, finishing third at the National Championships in June, although his form has gradually improved in recent weeks.

He recorded an encouraging season’s best of 13.09 to win in Paris. However, he suffered a setback in his last pre-Moscow outing in London at the end of last month, crashing out at the midway stage of the final, so his current shape is difficult to assess.

Merritt’s countryman Jason Richardson is bidding to become the third man in history, after compatriots Greg Foster and Allen Johnson, to mount a successful defence of this hurdles title following his success in Daegu two years ago.

We have not yet seen the best of the Olympic silver medallist so far in 2013. His season’s best time stands at a relatively modest 13.20 and his last victory came in Shanghai.

The US challenge is further bolstered by a resurgent David Oliver, the fastest man in the world this year with 13.03.

Oliver, the fourth fastest man in history and former US record-holder with 12.89, has shaken off the calf problems which bedevilled him during 2011 and 2012. With Diamond League wins behind him in Lausanne and London he should also be among the contenders again after finishing a frustrating fourth at the 2011 World Championships.

The four-strong US contingent is completed by Ryan Wilson, the surprise winner of the US Championships.

The 32-year-old ran 13.08 in Des Moines to make his first major championship team and should not be discounted, although he could place no higher than fourth during his three Diamond League outings in July.

He ran a national record of 13.05 to win in Eugene, which marked him out as a genuine gold medal threat in Moscow.

However, in his next competition, Parchment twisted an ankle while warming up at his National Championships and he has not competed since. He is entered for Moscow but has obviously not enjoyed ideal preparation.

He is joined on the Jamaican team by national champion Andrew Riley and veteran Dwight Thomas, who makes his sixth World Championship appearance.

Another with questions marks against his current form is 21-year-old Cuban prodigy Orlando Ortega. Tipped as Cuba's next Dayron Robles, Ortega ran 13.08 behind Parchment in Eugene but had a hiatus from competition for more than a month and on his return to competitive action he failed to finish in London at the end of last month.

The 2009 World champion Ryan Brathwaite has been a modicum of consistency this season and set a confidence-boosting Barbados record of 13.14 in Paris. Coupled with a good championship record, he could be in the mix again.

The European challenge is led by France’s World indoor bronze medallist Pascal Martinot-Lagarde, and the 21-year-old made a huge advance by setting a personal best 13.12 in Paris. His older brother, Thomas, with a best of 13.26 is also entered.

Russia’s European outdoor (110m Hurdles) and indoor (60m Hurdles) champion Sergey Shubenkov of Russia will not want for home support and is capable of a good performance, having already run 13.19 this season.

Great Britain’s William Sharman set a best of 13.26 in London and has finished fourth and equal fifth, respectively, at the past two editions of the World Championships, and he could also feature.